Chapter 10 Liquids and solids.

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2 They are similar to each otherDifferent than gases.They are incompressible.Their density doesn’t change much with temperature.These similarities are dueto the molecules staying close together in solids and liquidsand far apart in gasesWhat holds them close together?

3 Intermolecular forcesInside molecules (intramolecular) the atoms are bonded to each other.Intermolecular refers to the forces between the molecules.Holds the molecules together in the condensed states.

5 Dipole - Dipole Remember where the polar definition came from?Molecules line up in the presence of a electric field. The opposite ends of the dipole can attract each other so the molecules stay close together.1% as strong as covalent bondsWeaker with greater distance.Small role in gases.

10 London Dispersion ForcesNon - polar molecules also exert forces on each other.Otherwise, no solids or liquids.Electrons are not evenly distributed at every instant in time.Have an instantaneous dipole.Induces a dipole in the atom next to it.Induced dipole- induced dipole interaction.

12 London Dispersion ForcesWeak, short lived.Lasts longer at low temperature.Eventually long enough to make liquids.More electrons, more polarizable.Bigger molecules, higher melting and boiling points.Weaker than other forces.

18 Beading If a polar substance is placed on a non-polar surface.There are cohesive,But no adhesive forces.

19 Viscosity How much a liquid resists flowing.Large forces, more viscous.Large molecules can get tangled up.Cyclohexane has a lower viscosity than hexane.Because it is a circle- more compact.

20 How much of these? Stronger forces, bigger effect. Hydrogen bondingDipole-dipoleLDFIn that orderH next to O,N, or FPolar moleculesAll molecules

21 Model of a Liquid Can’t see molecules so picture them as-In motion but attracted to each otherWith regions arranged like solids butwith higher disorder.with fewer holes than a gas.Highly dynamic, regions changing between types.

22 Phases The phase of a substance is determined by three things.The temperature.The pressure.The strength of intermolecular forces.

23 SolidsTwo major types.Amorphous- those with much disorder in their structure.Crystalline- have a regular arrangement of components in their structure.

24 CrystalsLattice- a three dimensional grid that describes the locations of the pieces in a crystalline solid.Unit Cell-The smallest repeating unit in of the lattice.Three common types.

28 The book drones on aboutUsing diffraction patterns to identify crystal structures.Talks about metals and the closest packing model.It is interesting, but trivial.We need to focus on metallic bonding.Why do metal atoms stay together?How their bonding affects their properties.

29 Solids There are many amorphous solids. Like glass.We tend to focus on crystalline solids.two types.Ionic solids have ions at the lattice points.Molecular solids have molecules.Sugar vs. Salt.

30 Metallic Bonds How atoms are held together in the solid.Metals hold onto their valence electrons very weakly.Think of them as positive ions floating in a sea of electrons.

31 Sea of Electrons + Electrons are free to move through the solid.Metals conduct electricity.+

40 Carbon- A Special Atomic SolidThere are three types of solid carbon.Amorphous- soot - uninteresting.Diamond- hardest natural substance on earth, insulates both heat and electricity.Graphite- slippery, conducts electricity.How the atoms in these network solids are connected explains why.

41 Diamond- each Carbon is sp3 hybridized, connected to four other carbons.Carbon atoms are locked into tetrahedral shape.Strong s bonds give the huge molecule its hardness.

42 Why is it an insulator?All the electrons need to be shared in the covalent bondsCan’t move around

43 Graphite is different.Each carbon is connected to three other carbons and sp2 hybridized.The molecule is flat with 120º angles in fused 6 member rings.The p bonds extend above and below the plane.

44 This p bond overlap forms a huge p bonding network.Electrons are free to move throughout these delocalized orbitals.Conducts electricityThe layers slide by each other.Lubricant

45 Molecular solids. Molecules occupy the corners of the lattices.Different molecules have different forces between them.These forces depend on the size of the molecule.They also depend on the strength and nature of dipole moments.

46 Those without dipoles. Most are gases at 25ºC.The only forces are London Dispersion Forces.These depend on number of electrons.Large molecules (such as I2 ) can be solids even without dipoles. (LDF)

47 Those with dipoles.Dipole-dipole forces are generally stronger than L.D.F.Hydrogen bonding is stronger than Dipole-dipole forces.No matter how strong the intermolecular force, it is always much, much weaker than the forces in bonds.Stronger forces lead to higher melting and freezing points.

49 Water is special Each molecule has two polar O-H bonds.Each molecule has two lone pair on its oxygen.HOd+

50 Water is special Each molecule has two polar O-H bonds.Each molecule has two lone pair on its oxygen.Each oxygen can interact with 2 hydrogen atoms.HOd+

51 Water is specialHOd+This gives water an especially high melting and boiling point.

52 Ionic SolidsThe extremes in dipole-dipole forces-atoms are actually held together by opposite charges.Huge melting and boiling points.Atoms are locked in lattice so hard and brittle.Every electron is accounted for so they are poor conductors-good insulators.Until melted or dissolved.

55 Vaporization is an endothermic process - it requires heat.Energy is required to overcome intermolecular forces.Responsible for cool beaches.Why we sweat.

56 Condensation Change from gas to liquid.Achieves a dynamic equilibrium with vaporization in a closed system.What is a closed system?A closed system means matter can’t go in or out.Put a cork in it.What the heck is a “dynamic equilibrium?”

57 Dynamic equilibriumWhen first sealed the molecules gradually escape the surface of the liquid

58 Dynamic equilibriumWhen first sealed the molecules gradually escape the surface of the liquidAs the molecules build up above the liquid some condense back to a liquid.

59 Dynamic equilibriumAs time goes by the rate of vaporization remains constantbut the rate of condensation increases because there are more molecules to condense.Equilibrium is reached when

63 Dish of HgVacuumPatm=760 torrA barometer will hold a column of mercury 760 mm high at one atm

64 Dish of HgVacuumPatm=760 torrA barometer will hold a column of mercury 760 mm high at one atm.If we inject a volatile liquid in the barometer it will rise to the top of the mercury.

65 WaterA barometer will hold a column of mercury 760 mm high at one atm.If we inject a volatile liquid in the barometer it will rise to the top of the mercury.There it will vaporize and push the column of mercury down.Patm=760 torrDish of Hg

66 Dish of Hg The mercury is pushed down by the vapor pressure.Water VaporThe mercury is pushed down by the vapor pressure.Patm = PHg + PvapPatm - PHg = Pvap= 24 torr736 mm HgDish of Hg

69 Mathematical relationshipln is the natural logarithmln = Log base ee = Euler’s number an irrational number like pDHvap is the heat of vaporization in J/mol

70 Mathematical relationshipR = J/K mol.Surprisingly this is the graph of a straight line.If you graph ln P vs 1/T

71 Mathematical relationshipThe vapor pressure of water is 23.8 torr at 25°C. The heat of vaporization of water is 43.9 kJ/mol. Calculate the vapor pressure at 50°CAt what temperature would it have a vapor pressure of 760 torr?

72 Changes of stateThe graph of temperature versus heat applied is called a heating curve.The temperature a solid turns to a liquid is the melting point.The energy required to accomplish this change is called the Heat (or Enthalpy) of Fusion DHfus

73 Water and Steam Water and IceHeating Curve for WaterSteamWater and SteamWaterWater and IceIce

77 Water Vapor Vapor Solid Water Liquid WaterIf the vapor pressure of the solid is higher than that of the liquid the solid will release molecules to achieve equilibrium.Solid WaterLiquid WaterWater Vapor Vapor

78 While the molecules of condense to a liquid.Solid WaterLiquid WaterWater Vapor Vapor

79 This can only happen if the temperature is above the freezing point since solid is turning to liquid.Solid WaterLiquid WaterWater Vapor Vapor

80 Water Vapor Vapor Solid Water Liquid WaterIf the vapor pressure of the liquid is higher than that of the solid, the liquid will release molecules to achieve equilibrium.Solid WaterLiquid WaterWater Vapor Vapor

81 While the molecules condense to a solid.Solid WaterLiquid WaterWater Vapor Vapor

82 The temperature must be below the freezing point since the liquid is turning to a solid.Solid WaterLiquid WaterWater Vapor Vapor

83 Water Vapor Vapor Solid Water Liquid WaterIf the vapor pressure of the solid and liquid are equal, the solid and liquid are vaporizing and condensing at the same rate. The Melting point.Solid WaterLiquid WaterWater Vapor Vapor

84 Boiling PointReached when the vapor pressure equals the external pressure.Normal boiling point is the boiling point at 1 atm pressure.Superheating - Heating above the boiling point.Supercooling - Cooling below the freezing point.

85 Phase Diagrams.A plot of temperature versus pressure for a closed system, with lines to indicate where there is a phase change.

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